Membrane permeable to aromatic products

ABSTRACT

A multilayer structure with improved permeation for atmospheric diffusion of aromatic products wherein the structure comprises: a permeable membrane wherein said permeable membrane comprises at least two polymeric layers wherein the polymer of each layer is independently selected from the group consisting of polyethylene, very low density polyethylene, low density polyethylene, ethylene methylacrylate copolymer; a release layer wherein said release layer comprises a nylon polymer or a ethylene vinyl alcohol copolymer wherein the release layer is adhered to most inner polymeric layer of the permeable member which comprises the permeable membrane and wherein the adhesion between release layer and the adjacent layer of the polymeric permeable membrane is a relatively weak bond compared to the bond between the layers of the polymeric permeable membrane; and an impermeable membrane wherein said impermeable membrane comprises one or more layers wherein the materials which comprise the individual layers of the impermeable membrane are independently selected from metal or foil and wherein said impermeable portion is laminated to said release layer.

This application is a continuation U.S. application Ser. No. 09/730,090,filed Dec. 5, 2000 now U.S. Pat. No. 6,638,591, which is a continuationof U.S. application Ser. No. 09/135,196, filed Aug. 17, 1998. now U.S.Pat. No. 6,358,577 which is a continuation-in-part of application Ser.No. 08/475,699, filed Jun. 7, 1995, now U.S. Pat. No. 5,804,264.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention pertains, generally to the field of permeablemembranes and packaging for volatile materials, such as fragrances andother aromatic products, and more particularly, to permeable multilayermembranes and packages, which allow the controlled release of aromaticproducts over a period of time. The package prevents the escape of thearomatic fragrance until the consumer desires to start the release ofthe fragrance by peeling back the package to expose the permeablemembrane.

2. Description of the Art

The controlled time release of very volatile substances, such asfragrances and other aromatic products, presents a number of packagingproblems. Room “air fresheners” or fragrances have usually been packagedin glass bottles or vials. The fragrance is released into the atmosphereby transmission through an absorbent wick, which is capped until thetime of use. However, glass bottles are bulky and breakable. It isgenerally not economical to package fragrances in small quantitiesinside glass containers, because the cost of the glass container ishigh.

One proposed alternative method of packaging room fragrances is to placea breakable glass vial within a plastic container formed of a materialthat is permeable to the vapors of the volatile fragrance. The userdeliberately breaks the glass vial to allow the fragrance liquid to seepinto the absorbent pad and the vapors from the liquid slowly diffuseinto the atmosphere through the permeable outer container. Thesecontainers may be subject to accidental breakage of the glass vialduring shipping and handling, as well as to a possible puncture of thecontainer by broken glass. The manufacturing costs are increased by theuse of the glass vial within the container.

Other fragrance dispensers utilize sealed packages, which are opened bypeeling back a covering foil to expose a perforated panel covering anabsorbent pad filled with the fragrance liquid. The costs of suchcontainers make them generally inappropriate for dispensing smallamounts of the fragrance. It is also somewhat difficult to obtaincontrolled release of the fragrance at a fairly constant rate over thelife of the product, because the liquid is directly exposed to theatmosphere. In addition, the consumer may come into contact with thefragrance liquid, because the fragrance liquid may seep through theholes in the perforated panel.

Many other common packaging materials, including some plastic films, arepermeated by the fragrance before the desired release or are subject toattack by the fragrance itself or by its liquid carrier.

U.S. Pat. No. 4,634,614 issued to Holzner, relates to a peel system fora device for perfuming ambient air. The peel system comprises adelamination of a paper layer to separate a non-permeable lidding from apermeable membrane. In this invention, the paper layer does not providea barrier to the aromatic product and some of the aromatic product isallowed to escape with time. In addition, the exposed membrane often hasa poor appearance, as paper fibers may be left on the membrane when thepackage is peeled to activate the fragrance.

U.S. Pat. No. 4,145,001 issued to Weyenberg et al., and incorporatedherein by reference, discloses a dispenser having a permeable membrane.The fragrance is sandwiched between the inner layers of two heatsealable panels. One of the inner layers is permeable to the fragrancevapors. The outer layers of the panels are impermeable to the fragranceand its vapors. The dispenser is opened by peeling back a panel along arelease layer to expose the inner permeable layer. However, thepermeable membrane layer disclosed in U.S. Pat. No. 4,145,001 haslimited permeation for certain fragrances.

Other problems associated with permeable membranes are problems withmachine operations. The most effective resins for permeation are oftentacky in nature. The tacky nature of these resins often cause problemswith the operation of the package machinery and processing steps, suchas laminating, slitting and converting.

One objective of the present invention is an improved permeablemultilayer membrane that provides greater controlled release over anextended period of time and increased permeation for a broader range offragrances. Another objective is a multilayer membrane, which allows forthe special selection of resins in the machine and tie layers to preventproblems associated with the operation of the package machinery andprocessing steps. Another objective of the present invention is toprovide packaging for the fragrances and a means for exposing themembrane to the atmosphere at a desired time by consumer manipulation. Astill further objective is to provide a release layer that has improvedbarrier to fragrances.

SUMMARY

This invention relates to an improved permeable membrane for volatilesubstances, such as a room air fresheners, fragrances and other aromaticproducts, that satisfies the need for a permeable membrane whichprovides greater controlled release and increased permeation for a broadrange of fragrances. This invention also relates to the packaging of theimproved permeable membrane and to provide a means for exposing themembrane to the atmosphere at a desired time by consumer manipulation.This invention also relates to an improved release layer that aids incontaining the fragrance until the packaging is opened.

In one embodiment of the present invention, the invention is acoextruded multilayer structure comprising a permeable membrane and arelease layer. The membrane comprises a first permeable sealable layer,a second permeable layer. The release layer is adhered to the secondlayer. The adhesion between the release layer and the second layer is arelatively weak bond compared to the bond between the first and secondlayers. The bond strength is controlled by the selection of the resinsin the second layer and the release layer.

The first layer includes polymers, such as polyethylene, poly(ethylenevinyl acetate) (EVA) and other heat sealable permeable resins. Thesecond layer includes polymers such as polyethylene, poly(ethylene vinylacetate) and others that can be blended or modified to produce a strongbond to the first layer and a relatively weak bond to the release layer.The release layer includes a polymer or copolymer such as nylon orethylene vinyl alcohol copolymer (EVOH).

The ethylene vinyl alcohol of the present invention has a ethylenecontent of less than forty percent. The nylons of the present inventioninclude poly-(ε-caprolactam)/nylon-6; and poly(hexamethylene)/nylon-6,6.

In another embodiment of the present invention, the invention is acoextruded multilayer structure comprising a permeable membrane and arelease layer. The membrane comprises a first permeable sealable layer,a second permeable layer adhered to the first layer and a thirdpermeable layer adhered to the second layer. The release layer isadhered to the third layer. The adhesion between the release layer andthe third layer forms a relatively weak bond as compared to the adhesionbetween the first and second layers and the adhesion between the secondand third layers.

The first layer includes a polymer, such as polyethylene, (poly(ethylenevinyl acetate) (EVA) and other heat sealable permeable resins. Thesecond layer comprises semi crystaline polymers. The third layer isselected from resins that provide a high (strong) degree of bond to thesecond layer and controllable relatively weak bond to the release layer.The release layer includes a polymer, or copolymer such as nylon or EVOHresins.

In another embodiment of the present invention, the invention is acoextruded multilayer structure comprising a permeable membrane and arelease layer. The membrane comprises a first permeable sealable layer,a second permeable layer adhered to the first layer, a third permeablelayer adhered to the second layer and a fourth permeable layer adheredto the third layer. The release layer is adhered to the fourth layer.The adhesion between the release layer and the fourth layer forms arelatively weak bond as compared to the adhesion between the first andsecond layers, the adhesion between the second and third layers and theadhesion between the third and fourth layers. The release layer alsocooperates with the impermeable layers to contain the product.

The first layer includes a polymer, such as polyethylene, EVA blendsincluding very low density polyethylene (VLDPE) and other heat sealableresins. The second and fourth layers are selected from resins thatprovide a high degree of bond to the first and third layers and acontrollable relatively weak bond to the release layer. The third layercomprises resins with high permeability to gases and aromatic compounds.The release layer includes a polymer, such as a homopolymer or copolymerof nylon or EVOH.

In another preferred embodiment of the invention, the coextrudedmultilayer structure is incorporated into a package. The package holdsan aromatic product between two heat sealable panels. One of the panelscan be manipulated to remove certain impermeable layers to expose apermeable membrane to the atmosphere, which allows for the escape of thevapors from the aromatic product.

The first heat sealable panel is a laminated structure. It comprises apermeable membrane, a release layer and an impermeable portion. Thepermeable membrane comprises a first permeable sealable layer, a secondpermeable layer adhered to the first layer and a third permeable layeradhered to the second layer. The release layer is adhered to the thirdlayer of the permeable membrane. The release layer is relativelyimpermeable to most products and cooperates with the impermeable layersto contain the product.

The impermeable portion comprises one or more impermeable layers and isselected to be impermeable to the aromatic product and its vapors, sothat no significant amount of vapors will escape while the package issealed. The impermeable portion is laminated to the release layeropposite the permeable membrane.

The second heat sealable panel is a laminated structure comprising oneor more impermeable layers, which are selected to be impermeable to thearomatic product and its vapors, so that the vapors will not escapewhile the package is sealed.

The aromatic product is disposed between the first sealable layer of themembrane in the first heat sealable panel and an outer layer of thesecond heat sealable panel. The first sealable layer of the membrane andthe outer layer of the second panel are heat sealed together in a bondformed around the aromatic product.

The heat bonding around the aromatic product is preferably accomplishedby pressing all of the layers of the package between a hot die and aresilient backing. In such a case, the release layer of the first heatsealable panel is selected of a material which will form only a weakheat bond with the third permeable layer of the membrane. The adhesionof the weak heat bond is substantially less than the adhesion of thebond between the second and third layers of the membrane and the firstand second layers of the membrane. The adhesion of the bond is also lessthan the adhesion of the bond between the first sealable layer of themembrane and the outer layer of the second panel.

Preferably, the first sealable layer of the membrane and the outer layerof the second panel are not adhered together, except at the heat bondarea. This allows the layers of the package to be easily pulled awayfrom each other by the user between the two heat sealable panels up tothe area of the bond. As the package is pulled by the user to the areaof the heat bond, the first sealable layer of the membrane will split atthe heat bond and remain bonded to the outer layer of the second panel.The release layer will part from the third layer of the membrane toallow the release layer and the impermeable layers of the first heatsealable panel to be removed. This leaves the aromatic product coveredon one side by only the permeable membrane and allows the vapors fromthe aromatic product to diffuse through the permeable membrane into theatmosphere at a fairly constant rate over a period of time.

The process of heat bonding the layers of the package together ispreferably accomplished by using a die having a lip or protrusionextending slightly beyond the face of the remainder of the die. Whensuch a die is pressed onto the package layers and against a resilientbacking, the first sealable permeable layer of the membrane and theouter layer of the second panel will soften and spread apart from theline of the protrusion on the die to form a line of weakness. This lineof weakness is advantageous in allowing the membrane to split easily asthe package is peeled open by a user. To ensure the structural integrityof the package, it is preferable that the impermeable layers are formedof a material which will not melt at the temperature of the bonding die.

For optimum performance of the package, it is also preferred that theline of weakness, and the wider heat bond adjacent to it, be formed in aV or a chevron shape at a position spaced away from one end of thepackage. The user easily peels open the package up to the point of thechevron, with the weakened permeable layers splitting at the chevron toallow the remainder of the package to be peeled apart. The remainder ofthe heat seal surrounding the aromatic product is sealed over a broadarea without forming a line of weakness.

The package of this invention has the desirable feature of beingrelatively light and has no breakable parts, which could be dangerous.The package is very inexpensive to manufacture and is suitable fordispensing small quantities of fragrances. As long as the packageremains sealed, the volatile fragrance cannot escape; thus, allowing avery long shelf life for the product. Special precautions during thehandling of the product are unnecessary, since there are no parts thatcan be broken or easily damaged. Once the package has been opened by theconsumer, the volatile vapors diffuse through the permeable membrane ata controlled and selected rate. Because the process of transfer throughthe permeable layer is a diffusion process, rather than directevaporation, the rate of release of the vapor is relatively uniform overthe expected life of the package.

In a preferred process for producing the package, the layers of thepermeable membrane and the release layer are cast coextruded to form avery uniform but weak bond between the membrane and the release layer.The impermeable portion of the first panel is then adhered to therelease layer using an adhesive, which provides a long lasting anduniform bond between the two materials. The two heat sealable panels maythen be brought together over the aromatic product with a heated diebeing impressed over the two panels of the package to form a heat bondbetween them that surrounds and seals the aromatic product. Variousmaterials, such as metal foil, may be used for the impermeable portion,and in such case it is desirable to protect the outer surface of thefoil layer(s) by adhering a tough protective layer thereto.

In the case of some aromatic products the release layer can be selectedto have sufficient barrier to the product to eliminate the need for foilor other high barrier layers in the non-permeable portion of the toppanel. The panel is typically constructed with reverse printedpolyethylene tertphthalate (PET) film as the outer most layer. A barrierlayer located between the permeable membrane layers and the printedsurface is required not only to contain the produce prior to use butdually protects the printing from product attack. The barrierrequirement is a function of the chemical formulation of the product andthe required shelf life prior to use. Certain products contain fragranceoils or carriers such as iso-par that permeate more readily than otherformulations and thus require greater barrier. This is particularly trueif the product must be contained for 1-2 years before use.

In another preferred embodiment of the present invention, the coextrudedmultilayer structure is incorporated into a package. The package holdsan aromatic product between two heat sealable panels. A first heatsealable panel can be manipulated to remove certain impermeable layersto expose a permeable membrane to the atmosphere, which allows for theescape of the vapors from the aromatic product. The first heat sealablepanel comprises a four layer permeable membrane, a release layer-whichis somewhat impermeable and an most impermeable portion. The impermeableportion comprises one or more impermeable layers. The permeable membranecomprises a first permeable sealable layer, a second permeable layeradhered to the first layer, a third permeable layer adhered to thesecond layer and a fourth permeable layer adhered to the third layer.The release layer is adhered to the fourth layer of the permeablemembrane and the, impermeable portion is laminated to the release layeropposite the permeable membrane.

A second heat sealable panel is a laminated structure comprising one ormore impermeable layers, which are selected to be impermeable to thearomatic product and its vapors, so that the vapors will not escapewhile the package is sealed.

The aromatic product is disposed between the first sealable layer of themembrane in the first heat sealable panel and an outer sealable layer ofthe second heat sealable panel. The first sealable layer of the membraneand the outer layer of the second panel are heat sealed together in abond formed around the aromatic product.

In another preferred embodiment of the invention, the second heatsealable panel comprises a thermoform tray. The first sealable layer ofthe membrane is heat sealed to the thermoform tray to cover the tray.

These and other features, aspects and advantages of the presentinvention will be apparent from the following detailed description,appended claims and accompanying drawings showing preferred embodimentsof the present invention.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be further described in connection with theaccompanying drawings, in which:

FIG. 1 a & FIG. 1 b are cross-sections of embodiments of a multilayerstructure of this invention.

FIG. 2 is a cross-section of another embodiment of a multilayerstructure of this invention.

FIG. 3 is a cross-section of a package, in accordance with thisinvention.

FIG. 4 is a cross-section of another package, in accordance with thisinvention.

FIG. 5 is an exterior perspective view of a package, in accordance withthis invention.

FIG. 6 is an exterior perspective illustrating opening function.

DESCRIPTION

Referring to the drawings, an embodiment of the invention is showngenerally in FIG. 1 a. The multilayer structures comprises a firstsealable permeable layer 10, a second permeable layer 11 adhered to thefirst layer 10 and a release layer 12 adhered to the second layer 11.Layers 10 and 11 form the permeable membrane. Layer 12 is coextrudedwith the membrane layers and has two functions. First as the releaselayer it cooperates with the permeable layers to provide a designed peelor delamination. Second, the release layer offers a barrier to thearomatic product.

Layer 10 is permeable and cooperates with layer 11 to provide thedesired permeability of the membrane. Layer 10 comprises polymers andother components that provide permeability properties, good heat sealproperties and machinability. Examples of materials that are suitablefor layer 10, include polyethylene, EVA, poly(ethylene vinylacetate) orother sealable resins. Machine aids, such as slip and antiblock may alsobe added to this layer.

Layer 11 is a permeable layer that forms a tie between layers 10 and 12.Layer 11 is formed of resins that form a strong bond to layer 10 and thedesired relatively weak bond to layer 12. Examples of materials that aresuitable for layer 11, include: polyethylene, EVA, or other modifiedresins such as those modified with maleic anhydride. In a preferredembodiment, layer 12 is nylon or EVOH and layer 11 is a blend of LDPEand a modified polyolefin such as those sold by Equistar under the tradename “Plexar” or those sold by Mitsui under the trade name, “ADMER”.

Layer 12 is the release layer and cooperates with layer 11 to form thepeel function. Layer 12 provides barrier to the aromatic product. Therelease layer 12 may be homopolymer or copolymers of nylon or EVOH.Layers 10 and 11 form the membrane and in one example can have athickness of 4.0 mils and the release layer a thickness of 1.0 mil.

FIG. 1 b shows and alternate embodiment that provides an additionalmembrane layer that allows greater flexibility in choosing resins forparticular functions. The multilayer structure comprises a firstsealable permeable layer 10, a second permeable layer 11 adhered to thefirst layer 10, a third permeable layer 12 adhered to the second layer11 and a release layer 13 adhered to the third layer 12. Layers 10, 11and 12 form the permeable membrane. Layer 13 is coextruded with thepermeable membrane layers and has two functions. First as the releaselayer it cooperates with the permeable layers to provide a designed peelor delamination. Second, the release layer offers a barrier to thefragrance.

Layer 10 is permeable and cooperates with layers 11 and 12 to providethe desired permeability of the membrane. Layer 10 comprises polymersand other components that provide permeability properties, good heatseal properties and good machinability to the outside layer of themembrane. Examples of materials that are suitable for layer 10, include:polyethylene, EVA or other heat sealable resins. Machine aids, such asantiblock and slip, may also be added to this layer.

Layer 11 forms the bulk of the membrane and has the greatest impact onthe permeability of the membrane. Layer 11 is formed of resins having ahigh permeation rate for the aromatic product. Examples of materialswhich are suitable for layer 11, include: low density polyethylene(LDPE), very low density polyethylene (VLDPE), EVA, ethylene-methylacrylate copolymer and other available polymers, particularly semicrystaline polymers. Polymers of VLDPE having a density range between0.870 g/cc and 0.900 g/cc are especially preferred. Layer 11 may alsoinclude blends of these polymers designed for specific diffusion.

Heat of fusion measurements aid in identifying candidate polymers forlayer 11, because the heat of fusion data correlates with the gastransmission rates of the polymers. The heat of fusion measurements areobtained from pressed films using a Differential Scanning Calorimeter.Polymers with lower heats of fusion are less crystaline and have higherpermeation rates. See Table I.

TABLE I Heat of Fusion Samp. Supplier Type Grade (1^(st) Heat), J/g FDow-DuPont Engage Octene 8200 22.2 Plastomer I Exxon Exact 4011 38.6 GChevron Plastomer 2205 40.9 H Chevron Plastomer 2255 43.1 G Union Carb.VLDPE 9042 57.5 A Exxon Exact 3027 68.2 D Dow Affinity SSC 58000.01 68.5LLDPE B Exxon Exact 3028 73.5 E Dow Attain ULDPE 61512.13 78.2 C ExxonExact 3006 84.9

The degree of permeability of a particular polymer material can beincreased by adding impurities, such as calcium carbonate to open upadditional spaces between the polymer and the filler. The impurities areadded to the polymer material before the membrane is formed. Additionalpermeability may also be a by-product of coloring the layer byintroducing solid micro particles of pigment, which also tends to openup spaces between the polymer and the filler.

Layer 12 is a permeable tie layer. Layer 12 cooperates with layer 11 toprovide the desired permeation. Layer 12 is formed from resins thatprovide a strong bond with layer 11 and a relatively weak bond with therelease layer 13 to produce a peel laminate. Selection of the polymerfor layer 12 depends upon the polymer selection for layer 13.

In preferred embodiment, layer 13 is nylon or EVOH and layer 12 is ablend of LDPE and a modified polyolefin sold by Equistar under the tradename “PLEXAR” or “ADMER” sold by Mitsui.

Layer 13 is the release layer. Layer 13 cooperates with layer 12 to formthe peel function. Layer 13 also provides good barrier properties fromthe product. The release layer 13 is EVOH or nylon resins.

Layers 10 and 12 are relatively thin as compared to layer 11. In apreferred example, layer 10 is 0.5 mils to 1.0 mils, layer 12 is 0.5mils to 1.0 mils and layer 11 is 2.0 mils to 4.0 mils.

The third permeable layer 12 is initially uniformly bonded to a releaselayer 13 which is composed of a material that does not form strong heatbonds with the third permeable layer 12 at the same temperature at whichbonds are formed between permeable layers 10 and 11 and permeable layers11 and 12. For example, Nylon or EVOH can be utilized as the releaselayer in conjunction with modified polyethylene or EVA in the thirdpermeable layer. It is further desired to coextrude the permeablemembrane layers and the release layer together at a temperature thatproduces a very uniform but weak bond between the release layer and thepermeable membrane.

Referring to the drawings, an alternative embodiment of the invention isshown generally in FIG. 2. The multilayer structure comprises a firstsealable permeable layer 10, a second permeable layer 12 b adhered tothe first layer 10, a third permeable layer 11 adhered to the secondlayer 12 b, a fourth permeable layer 12 a adhered to the third permeablelayer 11 and a release layer 13 adhered to the fourth layer 12 a. Layers10, 11, 12 a and 12 b form the permeable membrane. Layer 13 iscoextruded with the permeable membrane layers and forms the releaselayer.

Layer 10 is permeable and cooperates with layers 12 b, 11 and 12 a toprovide the desired permeability for the membrane. Layer 10 comprisespolymers and other components that provide permeability properties, goodheat seal properties and good machinability to the outside layer of themembrane. Examples of materials that are suitable for layer 10, include:polyethylene, poly(ethylene vinyl acetate), very low densitypolyethylene, or other heat sealable resins or blends of same. Machineaids, such as processing aid, stabilizers, antiblock and slip, may alsobe added to this layer.

Layer 11 forms the bulk of the membrane and has the greatest impact onthe permeability of the membrane. Layer 11 is formed of resins having ahigh permeation rate for the aromatic product. Examples of materialswhich are suitable for layer 11, include: LDPE, VLDPE, EVA,ethylene-methyl acrylate copolymer and other available polymers,particularly semi crystaline polymers. Polymers of VLDPE having adensity range between 0.870 g/cc and 0.900 g/cc are especiallypreferred. Layer 11 may also include blends of these polymers.

Layers 12 a and 12 b cooperate with layer 11 to provide the desiredpermeability. Layers 12 a and 12 b are connected internally in theextrusion equipment and are comprised of the same material. Layers 12 aand 12 b are formed from resins that provide a strong bond to layer 11and a relatively weak bond to the release layer 13 to produce a peellaminate. Selection of the polymer for layers 12 a and 12 b depend uponthe polymer selection for layer 13. In a preferred embodiment of theinvention, layer 13 is nylon or EVOH and layers 12 a and 12 b arecomprised of a modified polyolefin. In another preferred embodiment,layer 13 is nylon or EVOH and layers 12 a and 12 b are a blend of LDPEand a tie resin e.g. that sold under the trade name “PLEXAR” or a Mitsuiresin sold under trade name “ADMER.”

Layer 13 is the release layer. Layer 13 cooperates with layer 12 a toform the peel function. Layer 13 also provides good barrier propertiesfrom the product. The release layer 13 may be EVOH or nylon orcopolymers of these resins.

The fourth permeable layer 12 a is initially uniformly bonded to arelease layer 13. The release layer 13 is comprised of a material thatdoes not form strong heat bonds with the fourth permeable layer 12 a atthe same temperature at which bonds are formed between permeable layers10 and 12 b, permeable layers 12 b and 11 and permeable layers 11 and 12a. For example, nylon or EVOH can be utilized as the release layer inconjunction with a modified polyethylene or EVA fourth permeable layer.It is further desired to coextrude the permeable membrane layers and therelease layer material together at a fairly low temperature thatproduces a very uniform but weak bond between the release layer and thepermeable membrane.

Another preferred embodiment of the invention is shown in FIG. 3. FIG. 3shows the incorporation of a multilayer permeable membrane into a scentrelease package. The package comprises two heat sealable panels 01 and02. Panel 01 comprises a permeable membrane, a release layer andimpermeable portion. The permeable membrane is formed by layers 10, 11and 12. Layer 13 is the release layer. The impermeable portion iscomprised of Layers 14, 15, 16 and 17.

The membrane comprises a first sealable permeable layer 10, a secondpermeable layer 11 adhered to the first layer 10 and a third permeablelayer 12 adhered to the second layer 11. The release layer 13 is adheredto the third layer 12. Layer 13 is coextruded with the permeablemembrane layers.

Layer 10 is permeable and cooperates with layer 11 to provide thedesired permeability. Layer 10 comprises polymers and other componentsthat provide permeability properties, good heat seal properties and goodmachinability to the outside layer of the membrane. Layer 10 is incontact with the aromatic product 30 and the material selected for layer10 should have minimum interaction with the product 30. Examples ofmaterials that are suitable for layer 10, include: polyethylene blendswith VLDPE EVA other heat sealable resins. Machine aids, such asantiblock, slip, and stabilizers may also be added to this layer.

Layer 11 forms the bulk of the membrane and has the greatest impact onthe permeability of the membrane. Layer 11 is formed of resins having ahigh permeation rate for the aromatic product. Examples of materialswhich are suitable for layer 11, include: LDPE, VLDPE, EVA,ethylene-methyl acrylate copolymer and other available polymers,particularly semi crystaline polymers. Polymers of VLDPE having adensity range between 0.870 and 0.900 g/cc are especially preferred.Layer 11 may also include blends of these polymers.

Layer 12 is a permeable tie layer. Layer 12 cooperates with layer 11 toprovide the desired permeation. Layer 12 is formed from resins thatprovide a strong bond to layer 11 and a relatively weak bond to therelease layer 13 to produce a peel laminate. Selection of the polymerfor layer 12 depends upon the polymer selection for layer 13. In apreferred embodiment of the invention, layer 13 is a nylon or EVOH andlayer 12 is a modified polyolefin. In another preferred embodiment,layer 13 is a nylon or EVOH and layer 12 is a blend of LDPE and a tieresin, e.g., those sold under the trade names “PLEXAR” or “AMER”.

Layer 13 is the release layer. Layer 13 cooperates with layer 12 to formthe peel function. Layer 13 also provides barrier properties to theproduct. The release layer 13 may be copolymer or homopolymer of nylonor EVOH

Layers 10 and 12 are relatively thin as compared to layer 11. In apreferred example, layer 10 is 0.5 to 1.0 mils, layer 12 is 0.5 to 1.0mils and layer 11 is 2.0 to 4.0 mils.

The third permeable layer 12 is initially uniformly bonded to a releaselayer 13. Release layer 13 comprises a material that does not formstrong heat bonds with the third permeable layer 12 at the sametemperature at which bonds are formed between permeable layers 10 and 11and permeable layers 11 and 12. For example, nylon or EVOH can beutilized a the release layer in conjunction with a modified polyethyleneor EVA in the third permeable layer. It is further desired to coextrudethe permeable membrane layers and the release layer together at atemperature that will produce a very uniform but weak bond between therelease layer and the permeable membrane.

Layers 10, 11, 12 and 13 are cast coextruded and comprise a multilayerstructure. The structure is laminated to the impermeable portion ofpanel 01 at layer 13. The impermeable portion of panel 01 compriseslayers 14, 15, 16 and 17. These layers are laminated together such thatlayer 14 is adhered to layer 15, layer 15 is adhered to layer 16opposite layer 14 and layer 16 is adhered to layer 17 opposite layer 15.Layer 13 is laminated to layer 14 opposite layer 15.

In a preferred embodiment of the invention, the release layer 13 isnylon or EVOH and layer 14 is a laminating adhesive. Layer 15 is foil,layer 16 is a polyethylene laminating resin and layer 17 is a polyester.

Panel 02 is comprised of layers 20, 21, 22, 23 and 24. Layers 20, 21,and 22 form a multilayer nylon coextruded film. In a preferredembodiment, the nylon coextruded film has adhesive or tie layers oneither side (adjacent) of the nylon layer. Layer 23 is an adhesive andlayer 24 is a polyester, acrylonitrile polymer (BAREX) or a recycledpolyester sheet. The nylon coextruded film is laminated to layer 24 bythe adhesive layer 23.

The aromatic product 30 is held between layer 10 of panel 01 and layer20 of panel 02. Layer 10 is heat sealed to layer 20. The bond formedbetween layer 10 and layer 20 is stronger than the bond formed betweenlayer 12 and release layer 13.

Another preferred embodiment of the invention is shown in FIG. 4. FIG. 4shows the incorporation of a four layer permeable membrane into a scentrelease package. The package comprises two heat sealable panels 01 and02. Panel 01 comprises a permeable membrane, a release layer and animpermeable portion. The permeable membrane is formed by layers 10, 11,12 a and 12 b. Layer 13 is the release layer. The impermeable portion iscomprised of layers 14, 15, 16 and 17.

The permeable membrane comprises a first sealable permeable layer 10, asecond permeable layer 12 b adhered to the first layer 10, a thirdpermeable layer 11 adhered to the second layer 12 b, a fourth permeablelayer 12 a adhered to the third permeable layer 11 and a release layer13 adhered to the fourth layer 12 a. Layer 13 is coextruded with thepermeable membrane layers.

Layer 10 is permeable and cooperates with layers 11, 12 a and 12 b toprovide the desired permeability of the membrane. Layer 10 comprisespolymers and other components that provide permeability properties, goodheat seal properties and good machinability to the outside layer of themembrane. Layer 10 is in contact with the aromatic product 30 and thematerial selected for layer 10 should have minimum interaction with theproduct 30. Examples of materials that are suitable for layer 10,include: polyethylene, EVA or other heat sealable resins. Machine Aids,such as antiblock and slip, may also be added to this layer.

Layer 11 forms the bulk of the membrane and has the greatest impact onthe permeability of the membrane. Layer 11 is formed of resins having ahigh permeation rate for the aromatic product. Examples of materialswhich are suitable for layer 11, include: LDPE, VLDPE, EVA,ethylene-methyl acrylate copolymer and other available polymers,particularly more semi-crystaline polymers. Polymers of VLDPE having adensity range between 0.870 g/cc and 0.900 g/cc are especiallypreferred. Layer 11 may also include blends of these polymers.

Layers 12 a and 12 b cooperate with layer 11 to provide the desiredpermeability. Layers 12 a and 12 b are connected internally in theextrusion equipment and are comprised of the same material. Layers 12 aand 12 b are formed from resins that provide a strong bond to layer 11and a relatively weak bond to the release layer 13 to produce a peellaminate. Selection of the polymer for layers 12 a and 12 b depends uponthe polymer selection for layer 13.

In a preferred embodiment of the invention, layer 13 is a nylon or EVOHand layers 12 a and 12 b are comprised of a modified polyolefin. Inanother preferred embodiment, layer 13 is a nylon or EVOH and layers 12a and 12 b are a blend of LDPE and an adhesion promoting polyolefin,such as the modified polyolefin sold by Equistar under the trade namePLEXAR or ADMER sold by Mitsui.

Layer 13 is the release layer. Layer 13 cooperates with layer 12 a toform the peel function. Layer 13 also provides barrier properties fromthe product. The release layer 13 is EVOH or nylon or copolymers ofthese resins.

The fourth permeable layer 12 a is initially uniformly bonded to arelease layer 13. The release layer 13 is comprised of a material thatdoes not form strong heat bonds with the fourth permeable layer 12 a atthe same temperature at which bonds are formed between permeable layers10 and 12 b, permeable layers 12 b and 11 and permeable layers 11 and 12a. For example, nylon or EVOH can be utilized as the release layer inconjunction with a modified polyethylene or EVA fourth permeable layer.It is further desired to coextrude the permeable membrane layers and therelease layer material together at a fairly low temperature to provide avery uniform but weak bond between the release layer and the permeablemembrane.

Layers 10, 11, 12 a, 12 b and 13 are cast coextruded and comprise amultilayer structure that is laminated to the impermeable portion ofpanel 01. The impermeable portion of panel 01 comprises layers 14, 15,16 and 17. In one embodiment of the invention, layer 14 is a laminatingextrusion resin, layer 15 is a foil, layer 16 is a polyethylenelaminating resin and layer 17 is a polyester. In another preferredembodiment of the invention, the release layer 13 is bonded to layer 15with a curing adhesive, 14.

Panel 02 is comprised of layers 20, 21, 22, 23 and 24. Layers 20, 21 and22 form a nylon coextruded film. In a preferred embodiment, the nyloncoextruded film comprises adhesive layers between the nylon layers.Layer 23 is an adhesive and layer 24 is a polyester, or acrylonitrile(BAREX) polymer, or a recycled polyester sheet. The nylon coextrudedfilm is laminated to layer 24 by the adhesive layer 23.

The aromatic product 30 is held between layer 10 of panel 01 and layer20 of panel 02. Layer 10 is heat sealed to layer 20. The bond formedbetween layer 10 and layer 20 is stronger than the bond formed betweenlayer 12 a and release layer 13.

Referring to the drawings, a preferred embodiment of the presentinvention is a package for selectively providing controlled release ofvapors from an aromatic product, as shown generally in an exterior viewat 50 in FIG. 5. The package is shown in FIG. 5 in an unopenedcondition, in which the aromatic product is sealed within the package.The heat seal strip 51 surrounds the position of the aromatic productwithin the package. The package is opened by a user pulling apart thepackage at corners shown generally at 52 where the package has not beenheat sealed and where there exists an interface between two panels ofthe layers of the package, which may be easily parted. FIG. 6 shows apartially opened package. In FIG. 6, 53 refers to the heat seal surfacesof the packages; 54 refers to the heat sealable panel 02; and 55 refersto the heat sealable panel 01.

The heat seal illustrated at 51 in FIG. 5 is formed to surround thearomatic product. However, it is not necessary that the entire bond beformed at the same time. For example, the V-shaped front and long sidesof the bond can be formed initially. The aromatic product is then placedin the pocket formed between the heat sealable panels 01 and 02. An endseal 51 b is then formed to complete the seal. The outer edge of theseal in general area 51 a has an impression formed in the membrane andsealant by a protrusion in the seal die. This impression or thinned areaaids in separation of the membrane and release layer as the panels areseparated at the chevron. The membrane, being tightly sealed to panel 02remains with panel 02, thus covering the product. It is apparent that anaromatic product can be deposited directly in the initially formedpocket and sealed and thus, eliminate the need for a carrier pad.

The multilayer structures, which include a permeable membrane and arelease layer, may be coextruded through any of several coextrusionmethods that are common in the art, including cast coextrusion.

The following examples are provided as illustrative of the invention,but should not be construed as being exhaustive or as limiting theinvention to the specific details thereof.

EXAMPLE 1

The multilayer structure was produced on a cast line. The first sealablepermeable layer of the membrane was formed from hot melting and castextruding 40 pounds per ream of a low density polyethylene, QuantumNA-206. The second permeable layer was formed of hot melting and castextruding 20 pounds per ream of a blend of 95% Quantum NA-204 LDPE and5% Quantum Plexar TR021, a maleic anhydride modified tie resin. Thepermeable layers were cast extruded with the release layers of 16 poundsper ream of Nylon 6, Allied 8207 at approximately 440° F. for thepermeable membrane layers and 490° F. for the nylon. The bond betweenthe LDPE in the second permeable layer and the nylon release layer wasbetween 25 and 100 grams per inch.

The cast multilayer film was adhesive laminated to the foil layer of anon-permeable structure. The non-permeable structure was produced byextrusion laminating 48 g PET to 35 g aluminum foil using 15 pounds perream of polyethylene. The completed structure thus provided a PET heatresistant outer layer, an aluminum barrier layer, a release layer and apermeable membrane.

Pouches were formed from two 2 inch by 5 inch panels of the laminatedstructure by heat sealing together the sealable membrane layers of thepanels on three sides using a hot ribbon impulse sealer. Each pouch wasfilled with approximately 5 cc of a test fragrance product and the openfourth side of the pouch sealed. Over the course of eighteen months, thepouches were inspected for integrity and the non-permeable layer ofvarious pouches was peeled away at the release layer to test functionand inspect condition of the membrane layer. Package performed asdesigned.

EXAMPLE 2

The multilayer structure is produced on a cast line. The first sealablepermeable layer of the membrane is formed from hot melting and castextruding 15 pounds per ream of a low density polyethylene, QuantumNA-206. The second permeable layer is formed from hot melting and castextruding 35 pounds per ream of very low density polyethylene, such as aFLEXOMER, which is a trade name of Union Carbide. The third permeablelayer is formed from hot melting and cast extruding 8 pounds per ream ofa low density polyethylene, tie layer blend. 95% NA-206 and 5% PLEXARTR021.

The permeable film is cast coextruded with the release layer of 16pounds per ream of a nylon, Allied 8207, at approximately 440° F. forthe low density polyethylene in the first permeable layer and 490° F.for the nylon. The bond between the low density polyethylene in thethird permeable layer and the nylon in the release layer is between 25and 10 g per 25.4 mm.

A seal is formed between the third permeable layer and the release layerby pressing the layers between a hot die and heated rubber backing onthe bottom using A die temperature of approximately 485° F. applied fora sufficient period of time for the heat bonds to form (approximately 1second.) The first permeable layer of the membrane was heat sealed to athermoformed tray containing an aromatic product.

Upon opening the package, by pulling the release layer apart from thethird permeable layer, the third permeable layer of low densitypolyethylene split apart uniformly along the line of weakness in aV-shape, leaving the membrane intact and sealed to the thermoformedtray. The fragrance could easily be detected, and a relatively uniformfragrance level was observed for a period of approximately 50 days afteropening.

The weight loss of the fragrance was compared to the weight loss of thefragrance using a standard film membrane. The standard membrane iscomprised of three permeable layers of a low density polyethylene. Theweight loss of the new film shows a quicker initial release of fragranceand more weight loss over time than the standard film.

EXAMPLE 3

The multilayer structure is produced on a cast line. The first sealablepermeable layer of the membrane is formed from hot melting and castextruding 18 pounds per ream of a blend of 65% by weight of a very lowdensity polyethylene, such as FLEXOMER, which is a tradename of UnionCarbide, and 35% by weight of a low density polyethylene, QuantumNA-206. The second permeable layer is formed from hot melting and castextruding 8 pounds per ream of a low density polyethylene, QuantumNA-206. The third permeable layer is formed from hot melting and castextruding 30 pounds per ream of a blend of 73% by weight of a very lowdensity polyethylene, such as Flexomer which is a trademark of UnionCarbide and 27% by weight of a low density polyethylene, Quantum NA-206.The fourth permeable layer is formed from hot melting and cast extruding8 pounds per ream of a low density polyethylene, Quantum NA-206.

The permeable film is cast coextruded with the release layer of 16pounds per ream of nylon, Allied 8207 at approximately 440° F. for thelow density polyethylene in the fourth permeable layer and 490° F. forthe nylon. The bond between the low density polyethylene in the fourthpermeable layer and the nylon in the release layer is between 25 g and100 g.

The coextruded structure contains approximately the followingdimensions: the release layer 1.0 mil, the fourth layer was 0.5 mil, thethird layer was 2.0 mil, the second layer was 0.5 mil and the firstsealable layer was 1.0 mil.

A seal is formed between the fourth permeable layer and the releaselayer by pressing the layers between a hot die and heated rubber backingon the bottom using a die temperature of approximately 485° F. appliedfor a sufficient period of time for the heat bonds to form(approximately 1 second). The first permeable layer of the membrane isheat sealed to a thermoformed tray containing an aromatic product.

Upon opening the package, by pulling the release layer apart from thethird permeable layer, the third permeable layer of low densitypolyethylene split apart uniformly along the line of weakness in aV-shape, leaving the membrane intact and sealed to the thermoformedtray. The fragrance could easily be detected, and a substantiallyuniform fragrance level was observed for a period of approximately 50days after opening.

The weight loss of the fragrance was compared to the weight loss of thefragrance using a standard film membrane. The standard membrane iscomprised of three permeable layers of a low density polyethylene. Theweight loss of the new film shows a quicker initial release of fragranceand, more weight loss over time than the standard film.

It is understood that the invention is not confined to the particularembodiments herein described as illustrative of the invention, butembraces all such modifications thereof as come with the scope of thefollowing claims.

1. A multilayer structure with improved permeation for atmosphericdiffusion of aromatic products, the structure comprising: (a) a firstpermeable layer comprising a blend of very low density polyethylene andlow density polyethylene; (b) a second permeable layer comprising lowdensity polyethylene; (c) a third permeable layer comprising a blend ofvery low density polyethylene and low density polyethylene; (d) a fourthpermeable layer comprising a material selected from the group consistingof a blend of low density polyethylene and a modified polyolefin; and(e) a release layer comprising ethylene vinyl alcohol copolymer whereinsaid second layer is adhered to said first layer, said third layer isadhered to said second layer, said fourth layer is adhered to said thirdlayer and said release layer is adhered to said fourth layer, whereinthe bond strength between said release layer and said fourth layer isless than the bond strength between said first and second layers, thebond strength between said second and third layers, and the bondstrength between said third and fourth layers; whereby said releaselayer is peeled apart from said fourth permeable layer when a force isapplied.
 2. A package with improved permeation for atmospheric diffusionof aromatic products the package, comprising a first heat sealable paneland a second heat sealable panel, said second panel having at least oneimpermeable layer; wherein said first heat sealable panel furthercomprises: (a) a permeable membrane having: (i) a first permeable layercomprising low density polyethylene, (ii) a second permeable layercomprising an semi crystaline polymer, wherein said second layer isadhered to said first layer, (iii) a third permeable layer comprising amaterial selected from the group consisting of: and a blend of lowdensity polyethylene and modified polyolefin, wherein said third layeris adhered to said second layer; (b) a release layer comprising ethylenevinyl alcohol copolymer, wherein said release layer is adhered to saidthird layer; and (c) an impermeable portion having at least oneimpermeable layer, wherein said impermeable portion is adhered to saidrelease layer; wherein the bond strength between said release layer andsaid third layer is less than the bond strength between said first andsecond layers, said second and third layers and said release layer andimpermeable portion, such that said release layer delaminates from saidthird permeable layer when a force is applied, and wherein said firstpermeable layer of said first panel is heat sealed to said second panel;whereby an aromatic product may be disposed between said first andsecond panel.
 3. A package as in claim 2, wherein said impermeableportion of said first panel comprises the following structure in order,(a) a laminating adhesive, (b) a foil layer, (c) a polyethylenelaminating resin, and (d) a polyester resin; wherein said laminatingadhesive layer adheres to said release layer.
 4. A package as in claim2, wherein said second heat sealable panel comprises the followingstructure, in order: (a) a nylon coextruded film; (b) an adhesive; and(c) a polyester film wherein said nylon coextruded film is heat sealedto said first permeable layer.
 5. A package with improved permeation foratmospheric diffusion of aromatic products the packaging comprising afirst heat sealable panel and a second heat sealable panel, said secondpanel having at least one impermeable layer; wherein said first heatsealable panel comprises: (a) a permeable membrane having, (i) a firstpermeable layer comprising a blend of very low density polyethylene andlow density polyethylene, (ii) a second permeable layer comprising lowdensity polyethylene, wherein said layer is adhered to said first layer,(iii) a third permeable layer comprising a blend of very low densitypolyethylene and low density polyethylene, wherein said third layer isadhered to said second layer, and (iv) a fourth permeable layercomprising a material selected from the group consisting of low densitypolyethylene and a blend of low density polyethylene and a modifiedpolyolefin, wherein said fourth layer is adhered to said third layer;(b) a release layer comprising ethylene vinyl copolymer; wherein saidrelease layer is adhered to said fourth layer; (c) an impermeableportion having at least one impermeable layer, wherein said impermeableportion is adhered to said release layer; wherein the bond strengthbetween said release layer and said fourth layer is less than the bondstrength between said first and second layers, said second and thirdlayers, said third and fourth layers and said release layer andimpermeable portion, such that said release layer delaminates from saidfourth layer when a force is applied, and wherein said first permeablelayer of said first panel is heat sealed to said second panel, wherebyan aromatic product may be disposed between said first and second panel.